Buggy code:
public class ResultCollector extends AbstractListenerElement implements Serializable , NoThreadClone , Clearable , Remoteable , SampleListener , TestListener { static final long serialVersionUID = 2 ; private static final String TESTRESULTS_START = "<testResults>" ; private static final String TESTRESULTS_START_V1_1 = ( "<testResults<seq2seq4repair_space>version=\"" + ( SaveService . version ) ) + "\">" ; private static final String TESTRESULTS_END = "<//testResults>" ; private static final String XML_HEADER = "<?xml<seq2seq4repair_space>version=\"1.0\"<seq2seq4repair_space>encoding=\"UTF-8\"?>" ; private static final int MIN_XML_FILE_LEN = ( ( ResultCollector . XML_HEADER . length ( ) ) + ( ResultCollector . TESTRESULTS_START . length ( ) ) ) + ( ResultCollector . TESTRESULTS_END . length ( ) ) ; private static transient Logger log = LoggingManager . getLoggerForClass ( ) ; public static final String FILENAME = "filename" ; public static final String SAVE_CONFIG = "saveConfig" ; public static final String ERROR_LOGGING = "ResultCollector.error_logging" ; private transient DefaultConfigurationSerializer serializer ; private volatile transient PrintWriter out ; private boolean inTest = false ; private static Map files = new HashMap ( ) ; private Set hosts = new HashSet ( ) ; protected boolean isStats = false ; public ResultCollector ( ) { } private void setFilenameProperty ( String f ) { } public String getFilename ( ) { } public boolean isErrorLogging ( ) { } public void setErrorLogging ( boolean errorLogging ) { } public void setFilename ( String f ) { } public void testEnded ( String host ) { } public void testStarted ( String host ) { } public void testEnded ( ) { } public void testStarted ( ) { } public void loadExistingFile ( ) throws IOException { } private static void writeFileStart ( PrintWriter writer , SampleSaveConfiguration saveConfig ) { if ( saveConfig . saveAsXml ( ) ) { writer . println ( ResultCollector . XML_HEADER ) ; writer . println ( ResultCollector . TESTRESULTS_START_V1_1 ) ; } else if ( saveConfig . saveFieldNames ( ) ) { <START_BUG> writer . println ( OldSaveService . printableFieldNamesToString ( ) ) ; <END_BUG> } } private static void writeFileEnd ( PrintWriter pw , SampleSaveConfiguration saveConfig ) { } private static synchronized PrintWriter getFileWriter ( String filename , SampleSaveConfiguration saveConfig ) throws IOException { } private static boolean trimLastLine ( String filename ) { } private void readSamples ( TestResultWrapper testResults ) throws Exception { } private Configuration getConfiguration ( String filename ) throws IOException , ConfigurationException , SAXException { } public void clearVisualizer ( ) { } public void sampleStarted ( SampleEvent e ) { } public void sampleStopped ( SampleEvent e ) { } public void sampleOccurred ( SampleEvent e ) { } protected void sendToVisualizer ( SampleResult r ) { } private void recordResult ( SampleResult result ) throws Exception { } private String getSerializedSampleResult ( SampleResult result ) throws IOException , ConfigurationException , SAXException { } public void recordStats ( TestElement e ) throws Exception { } private synchronized boolean isResultMarked ( SampleResult res ) { } private void initializeFileOutput ( ) throws IOException { } private synchronized void finalizeFileOutput ( ) { } public void testIterationStart ( LoopIterationEvent event ) { } public SampleSaveConfiguration getSaveConfig ( ) { } public void setSaveConfig ( SampleSaveConfiguration saveConfig ) { } }

Fix:
writer . println ( OldSaveService . printableFieldNamesToString ( saveConfig ) ) ;